Is there some special option/steps involved when unistalling OneAgent on SELinux

We installed OneAgent with the option -p to preserve policy sources

Ref FAQ.

How does the OneAgent affect SELinux-enabked systems ?

The OneAgent installation program modifies the SELinux security policy. It allows Dynatrace OneAgent to add its own library between the system and the monitored software.

We want to be as transparent as possible. You can use -p parameter to preserve policy sources (by default they are purged at the end of installation). With this parameter you can check what we do to ensure that your security policy isn't harmed. Go to /opt/dynatrace/SELinuxPolicy to investigate.